How do the full-generation poly(amido)amine (PAMAM) dendrimers activate blood platelets? Activation of circulating platelets and formation of "fibrinogen aggregates" in the presence of polycations

Effects and treatment applications of polymeric nanoparticles on improving platelets' storage time: a review of the literature from 2010 to 2020

Maintaining the quality of platelet products and increasing their storage time are priorities for treatment applications. The formation of platelet storage lesions that limit the storage period and preservation temperature, which can prepare a decent environment for bacterial growth, are the most important challenges that researchers are dealing with in platelet preservation. Nanotechnology is an emerging field of science that has introduced novel solutions to resolve these problems. Here, we reviewed the reported effects of polymeric nanoparticles-including chitosan, dendrimers, polyethylene glycol (PEG), and liposome-on platelets in articles from 2010 to 2020. As a result, we concluded that the presence of dendrimer nanoparticles with a smaller size, negative charge, low molecular weight, and low concentration along with PEGylation can increase the stability and survival of platelets during storage. In addition, PEGylation of platelets can also be a promising approach to improve the quality of platelet bags during storage.

Evaluation of the effects of nanoparticles on the therapeutic function of platelet: a review

OBJECTIVES

Nanotechnology and nanoparticles are used in different applications in disease monitoring and therapy in contact with blood. Nanoparticles showed different effects on blood components and reduced or improved the function of therapeutic platelet during the storage time. This review study was performed to evaluate the impacts of various sizes and charges of nanoparticles on platelet function and storage time. The present review contains the literature between 2010 and 2020. The data have been used from different sites such as PubMed, Wiley, ScienceDirect and online electronic journals.

KEY FINDINGS

From the literature survey, it has been demonstrated that among various properties, size and charge of nanoparticles were critical on the function of therapeutic platelet during the storage and inhibition of their aggregation. Overall, this study described that nanoparticles with smaller size and negative charge were more effective in increasing the survival time, inhibition of aggregation and improving the function of therapeutic platelet.

SUMMARY

Based on the current review, it can be confirmed that nanoparticles such as dendrimer, Au, Ag and iron oxide nanoparticles with smaller size and negative charge have significant advantages for improving the efficacy of platelets during the storage chain and inhibition of their aggregation.

Chiral Recognition of Homochiral Poly (amidoamine) Dendrimers Substituted with R- and S-Glycidol by Keratinocyte (HaCaT) and Squamous Carcinoma (SCC-15) Cells In Vitro

The generation 2 and 3 poly(amidoamine) dendrimers (PAMAM G2 and G3) were converted into N-(2,3-dihydroxy)propyl derivatives by the addition of enantiomerically pure S- and R-glycidol. The homochiral dendrimers bind to HaCaT and SCC-15 cell membranes with an R/S glycidol enantioselectivity ratio of 1.5:1, as was quantitatively determined by fluorescence microscopy and visualized by confocal microscopy. Fully substituted G2 and G3 dendrimers were equipped with 32 and 64 N-(2,3-dihydroxy)propyl residues and showed effectively radial symmetry for homochiral derivatives in ¹³C NMR spectrum in contrary to analogs obtained by reaction with rac-glycidol. The sub-stoichiometric derivatives of G2 and G3 were also obtained in order to characterize them spectroscopically. The homochiral dendrimers were labeled with two different fluorescent labels, fluorescein, and rhodamine B, using their isothiocyanates to react with G2 and G3 followed by the addition of S- and R-glycidol. Obtained fluorescent derivatives were deficiently filled with N-(2,3-dihydroxy)propyl substituents due to steric hindrance imposed by the attached label. Nevertheless, these derivatives were used to determine their ability to bind to the cell membrane of human keratinocytes (HaCaT) and squamous carcinoma cells (SCC-15). Confocal microscopy images obtained from cells treated with variously labeled conjugates and fluorescence analysis with fluorescence reader allowed us to conclude that R-glycidol derivatives were bound and entered the cells preferentially, with higher accumulation in cancer cells. The G3 polyamidoamine (PAMAM)-based dendrimers were taken up more efficiently than G2 derivatives. Moreover, S- and R-glycidol furnished dendrimers were highly biocompatible with no toxicity up to 300 µM concentrations, in contrast to the amine-terminated PAMAM analogs.

Intravital Assessment of Blood Platelet Function. A Review of the Methodological Approaches with Examples of Studies of Selected Aspects of Blood Platelet Function

Platelet biology owes to intravital studies not only a better understanding of platelets’ role in primary hemostasis but also findings that platelets are important factors in inflammation and atherosclerosis. Researchers who enter the field of intravital platelet studies may be confused by the heterogeneity of experimental protocols utilized. On the one hand, there are a variety of stimuli used to activate platelet response, and on the other hand there are several approaches to measure the outcome of the activation. A number of possible combinations of activation factors with measurement approaches result in the aforementioned heterogeneity. The aim of this review is to present the most often used protocols in a systematic way depending on the stimulus used to activate platelets. By providing examples of studies performed with each of the protocols, we attempt to explain why a particular combination of stimuli and measurement method was applied to study a given aspect of platelet biology.

Stepwise Glucoheptoamidation of Poly(Amidoamine) Dendrimer G3 to Tune Physicochemical Properties of the Potential Drug Carrier: In Vitro Tests for Cytisine Conjugates

Third-generation poly(amidoamine) dendrimer (PAMAM) was modified by stepwise primary amine group amidation with d-glucoheptono-1,4-lactone. The physicochemical properties of the conjugates—size, ζ potential in lysosomal pH 5 and in neutral aqueous solutions, as well as intramolecular dynamics by differential scanning calorimetry—were determined. Internalization and toxicity of the conjugates against normal human fibroblasts BJ were monitored in vitro in order to select an appropriate carrier for a drug delivery system. It was found that initial glucoheptoamidation (up to 1/3 of amine groups of neat dendrimers available) resulted in increase of conjugate size and ζ potential. Native or low substituted dendrimer conjugates accumulated efficiently in fibroblast cells at nontoxic 1 µM concentration. Further substitution of dendrimer caused consistent decrease of size and ζ potential, cell accumulation, and toxicity. All dendrimers are amorphous at 36.6 °C as determined by differential scanning calorimetry (DSC). The optimized dendrimer, half-filled with glucoheptoamide substituents, was applied as carrier bearing two covalently attached cytisine molecules: a rigid and hydrophobic alkaloid. The conjugate with 2 cytisine and 16 glucoheptoamide substituents showed fast accumulation and no toxicity up to 200 µM concentration. The half-glucoheptoamidated PAMAM dendrimer was selected as a promising anticancer drug carrier for further applications.

Diabetes and Hyperglycemia Affect Platelet GPIIIa Expression. Effects on Adhesion Potential of Blood Platelets from Diabetic Patients under In Vitro Flow Conditions

Blood platelets play a crucial role in the early stages of atherosclerosis development. The process is believed to require firm adhesion of platelets to atherosclerosis-prone sites of the artery. However, little evidence exists regarding whether the blood platelets of individuals with pathological conditions associated with atherosclerosis have higher potential for adhesion. This process is to a large extent dependent on receptors present on the platelet membrane. Therefore, the aim of the presented study was to determine whether blood platelets from diabetic patients have higher capacity of adhesion under flow conditions and how diabetes affects one of the crucial platelet receptors involved in the process of adhesion-GPIIIa. The study compares the ability of platelets from non-diabetic and diabetic humans to interact with fibrinogen and von Willebrand factor, two proteins found in abundance on an inflamed endothelium, under flow conditions. The activation and reactivity of the blood platelets were also characterized by flow cytometry. Platelets from diabetic patients did not demonstrate enhanced adhesion to either studied protein, although they presented increased basal activation and responsiveness towards low concentrations of agonists. Platelets from diabetic patients were characterized by lower expression of GPIIIa, most likely due to an enhanced formation of platelet-derived microparticles PMPs, as supported by the observation of elevated concentration of this integrin and of GPIIIa-positive PMPs in plasma. We conclude that altered functionality of blood platelets in diabetes does not increase their adhesive potential. Increased glycation and decrease in the amount of GPIIIa on platelets may be partially responsible for this effect. Therefore, higher frequency of interactions of platelets with the endothelium, which is observed in animal models of diabetes, is caused by other factors. A primary cause may be a dysfunctional vascular wall.

Influence cationic and anionic PAMAM dendrimers of low generation on selected hemostatic parameters in vitro

BACKGROUND

Polyamidoamine (PAMAM) dendrimers are a new class of monodisperse polymers that are used for drug delivery in systemic administrations. The influence of PAMAM dendrimers on components of the blood coagulation system has been extensively studied, but their effect on the activity of the fibrinolysis system has not been studied to date.

METHODS

The effect of cationic (G1-G3) and anionic (G1.5-G3.5) PAMAM dendrimers on the conformation and function of the main components of the coagulation and fibrinolysis systems was comparatively studied. Changes in overall plasma hemostatic potential, thrombin generation, prothrombin time, thrombin and tPA activities, the fluorescence of fibrinogen and plasminogen, zeta potential, polymerization of fibrinogen, and activation of plasminogen were analyzed to assess coagulofibrinolytic mechanisms of influence of the charge of the dendrimers.

RESULTS

Cationic dendrimers increased prothrombin time, suppressed thrombin generation in plasma, and changed the conformation and coagulability of fibrinogen, while anionic dendrimers did not have such effects. Anionic dendrimers slightly reduced tPA activity and altered plasminogen conformation much more strongly than the cationic dendrimers. Plasminogen activation by tPA was strongly inhibited by anionic dendrimers and weakly stimulated by cationic dendrimers. All these effects were enhanced with increasing generation and concentration of the dendrimers.

CONCLUSIONS

PAMAM-NH₂ dendrimers inhibit the extrinsic activation pathway of the coagulation system and alter the conformation and function of fibrinogen. PAMAM-COOH dendrimers change the conformation of plasminogen and inhibit its activation by tPA. This study gives new insight into the effect of anionic PAMAM dendrimers on the activity of the fibrinolytic system. For intravenous applications, the antifibrinolytic effect of anionic PAMAM dendrimers of generation ≥G2.5 should be considered.

Testosterone and dihydrotestosterone reduce platelet activation and reactivity in older men and women

The cardiovascular effects of testosterone and dihydrotestosterone are generally attributed to their modulatory action on lipid and glucose metabolism. However, no ex vivo studies suggest that circulating androgen levels influence the activation and reactivity of blood platelets - one of the main components of the haemostasis system directly involved in atherosclerosis. The levels of testosterone, dihydrotestosterone and oestradiol in plasma from men and women aged from 60 to 65 years were measured by LC-MS; the aim was to identify any potential relationships between sex steroid levels and the markers of platelet activation (surface membrane expression of GPII/IIIa complex and P-selectin) and platelet reactivity in response to arachidonate, collagen or ADP, monitored with whole blood aggregometry and flow cytometry. The results of the ex vivo part of the study indicate that the concentrations of testosterone and its reduced form, dihydrotestosterone are significantly negatively associated with platelet activation and reactivity. These observations were confirmed in an in vitro model: testosterone and dihydrotestosterone significantly inhibited platelet aggregation triggered by arachidonate or collagen. Our findings indicate that testosterone and dihydrotestosterone are significant haemostatic steroids with inhibitory action on blood platelets in older people.

Generation 2 (G2) - Generation 4 (G4) PAMAM dendrimers disrupt key plasma coagulation parameters

The aim of the research was to evaluate the effects of G2 - G4 PAMAM dendrimers on basic plasma haemostasis parameters (Partially Activated Thrombin Time (APTT), Prothrombin Time (PT), Thrombin Time (TT)) as well as the activity of factor X, antithrombin III (AT), protein C and plasmin. Furthermore, tissue factor (TF) synthesis in endothelial cells and viability of smooth muscle cells in the presence of PAMAM dendrimers was investigated. APTT, PT and TT were performed according to the available commercial methods. The activity of factor X was conducted based on deficient plasma factor X. Protein C, AT and plasmin activity were measured spectrophotometrically using chromogenic substrates. Intracellular TF production in human umbilical vein endothelial cells (HUVECs) was measured using immunohistochemical method. Viability of Human Aortal Smooth Muscle cells (hAoSMCs) was established using WST-1 assay. PAMAM dendrimers decreased activity of factor X, and concomitantly prolonged PT and APTT. We also demonstrated shortened TT and increased fibrinogen concentrations in plasma treated with G4 PAMAM dendrimers, suggesting formation of fibrinogen aggregates. G2 - G4 PAMAM dendrimers decreased the activity of both naturally occurring anticoagulants AT and protein C. G2 and G3 PAMAM dendrimers did not affect the proteolytic reaction with plasmin. PAMAM dendrimers were found not to trigger TF production in undisturbed endothelial cells. PAMAM dendrimers, depending on the concentration and generation decreased viability of AoSMCs. The results presented within the current study suggest complex but mostly undesirable effect of G2 - G4 PAMAM dendrimers on plasma haemostasis and underscore the need for further in-depth research.

Platelet and Red Blood Cell Counts, as well as the Concentrations of Uric Acid, but Not Homocysteinaemia or Oxidative Stress, Contribute Mostly to Platelet Reactivity in Older Adults

Purpose

The goal of this study was to estimate the hierarchical contribution of the most commonly recognized cardiovascular risk factors associated with atherogenesis to activation and reactivity of blood platelets in a group of men and women at ages 60-65.

Methods

Socioeconomic and anthropometric data were taken from questionnaires. Blood morphology and biochemistry were measured with standard diagnostic methods. Plasma serum homocysteine was measured by immunochemical method. Plasma concentrations of VCAM, ICAM, total antioxidant status, and total oxidant status were estimated with commercial ELISA kits. Markers of oxidative stress of plasma and platelet proteins (concentrations of protein free thiol and amino groups) and lipids (concentrations of lipid peroxides) and generation of superoxide anion by platelets were measured with colorimetric methods. Platelet reactivity was estimated by impedance aggregometry with arachidonate, collagen, and ADP as agonists. Expression of selectin-P and GPIIb/IIIa on blood platelets was tested by flow cytometry.

Results

Platelet aggregation associated significantly negatively with HGB and age and significantly positively with PLT, MPV, PCT, PDW, and P-LCR. When platelet reactivity (“cumulative platelet reactivity_aggregation”) was analyzed in a cumulated manner, the negative association with serum concentration of uric acid (R_s = −0.169, p = 0.003) was confirmed. Multivariate analysis revealed that amongst blood morphological parameters, platelet count, plateletcrit, and number of large platelets and uric acid are the most predictive variables for platelet reactivity.

Conclusions

The most significant contributors to platelet reactivity in older subjects are platelet morphology, plasma uricaemia, and erythrocyte morphology.

Identification of Candidate Biomarkers in Malignant Ascites from Patients with Hepatocellular Carcinoma by iTRAQ-Based Quantitative Proteomic Analysis

Almost all the patients with hepatocellular carcinoma (HCC) at advanced stage experience pathological changes of chronic liver cirrhosis, which generally leads to moderate ascites. Recognition of novel biomarkers in malignant ascites could be favorable for establishing a diagnosis for the HCC patients with ascites, and even predicting prognosis, such as risk of distant metastasis. To distinguish the proteomic profiles of malignant ascites in HCC patients from those with nonmalignant liver cirrhosis, an iTRAQ pipeline was built up to analyze the differentially distributed proteins in the malignant ascites from HCC patients (n=10) and benign ascites from hepatic decompensation (HD) controls (n=9). In total, 112 differentially distributed proteins were identified, of which 69 proteins were upregulated and 43 proteins were downregulated (ratio <0.667 or >1.3, respectively) in the malignant ascites. Moreover, 19 upregulated proteins (including keratin 1 protein and rheumatoid factor RF-IP20, ratio>1.5) and 8 downregulated proteins (including carbonic anhydrase 1, ratio<0.667) were identified from malignant ascites samples. Functional categories analyses indicated that membrane proteins, ion regulation, and amino acid metabolism are implicated in the formation of HCC malignant ascites. Pathways mapping revealed that glycolysis/gluconeogenesis and complement/coagulation cascades are the mostly affected cell life activities in HCC malignant ascites, suggesting the key factors in these pathways such as Enolase-1 and fibrinogen are potential ascitic fluid based biomarkers for diagnosis and prognosis for HCC.